Electrochemical devices such as lithium ion secondary batteries and electric double-layer capacitors have characteristics such as compact size, light weight, high energy-density, and the ability to be repeatedly charged and discharged, and are used in a wide range of applications.
For example, an electrode for a lithium ion secondary battery generally includes a current collector and an electrode mixed material layer (positive electrode mixed material layer or negative electrode mixed material layer) formed on the current collector. The electrode mixed material layer is formed, for example, by applying, onto the current collector, a slurry composition containing an electrode active material, a binder, a solvent, and so forth and drying the applied slurry composition.
In recent years, there have been attempts to improve slurry compositions used in the formation of electrode mixed material layers in order to further improve electrochemical device performance.
For example, JP 2015-213049 A (PTL 1) discloses the following technique: A polymer containing a vinyl cyanide unit and an acidic group-containing unit in respective predetermined proportions and having a weight-average molecular weight in a predetermined range is formed in water. The polymer is collected by suction filtration, washed with warm water, and then dried. Subsequently, the dried polymer is mixed with a positive electrode active material as an electrode active material, N-methylpyrrolidone as a solvent, and the like, to produce a slurry composition. According to PTL 1, by using this slurry composition, an electrode having excellent peel strength (adhesion strength between an electrode mixed material layer and a current collector) and flexibility can be produced to thus obtain a non-aqueous secondary battery with improved electrochemical stability.